The L6 line of cultured muscle cells will respond acutely to insulin by an increase in glucose uptake and glycogen synthesis. When certain clones of these cells are grown in the presence of insulin, the acute response to insulin is markedly impaired. This study will focus on the mechanism of this insulin-induced insulin antagonism by investigating insulin binding and glucose transport. Isolated hepatocytes from obese rats will be compared to those of lean animals in regard to the insulin effect on net incorporation of glucose-C14 to glycogen to determine if insulin antagonism in obesity extends to the liver in addition to its well known sites in muscle and fat.